1. Field of the Invention
The present invention relates to a method of production of a relief valve including a valve body, where the upper surface of the relief valve is flat, and where the flat upper surface of the relief valve is fixedly connected to a flat inner surface of a container.
2. Brief Description of the Background of the Invention Including Prior Art
Relief valves are well known in the art. However, the known relief valves exhibit too high a thickness, thereby causing deformations of the packaged product. Another drawback of the known relief valves is that the diameter of the relief valve is too large and results in difficulties when handling the flexible material onto which the relief valve is applied. In addition, the application of the known valve may encounter major difficulties during thermowelding and/or thermosealing if the valve is not made out of a sufficiently soft material. It was found that the insertion of a known valve into an already punched hole of a package including a packaged product or of a flexible container may present centering difficulties.
Other problems in regard to the known relief valves concern the external appearance, the possibility of tampering, and the stacking difficulties of packages. The good operation of the known valve is jeopardized and the quality of the packaged product can be endangered where the relief valve is applied to the outside of a package or where the relief valve is disposed inside the package and protrudes due to its shape to the outside of the package.
The German Patent document DE-A-3,147,321 discloses an embodiment of a relief valve, where the relief valve includes a valve body with venting holes and a peripheral groove, a circular disk with a valve hole and with a slanted edge fitted into the peripheral groove, a membrane resting on the seal seat of the valve body, and of a viscous layer provided between the membrane and the seal seat. The relief valve of the German Patent document DE-A-3,147,321 is thermosealed to the inside wall of a flexible container, where the flexible container is provided with a venting hole.
The German Patent document DE-A-3,125,496 teaches a pressure control valve for venting of packing containers, where the valve itself protrudes from the outer surface of the packing container.
The German Patent document DE-C-1,195,830 teaches a relief valve intended for use in conjunction with a battery closure and to form an integral part of a battery or accumulator.
The French Patent document FR-A-2,338,865 discloses a safety valve disposed in a container. The actuating member of the safety valve is formed by a pressure means preferably made of a polyurethane foam. The safety valve is actuated if the pressure inside the container attains a predefined value.
The actuating portion of the pressure relief valve disclosed in the UK Patent document GB 2,099,958 again is formed by a synthetic foam disk. The disadvantage of this pressure relief valve is that this relief valve is adhesively attached to the outside of a container and thereby preventing formation of a flat outer surface of the container.
The U.S. Pat. No. 4,271,241 discloses a resealable valve for containers such as batteries. This valve is similar to the relief valve taught in the German Patent document DE-C-1,195,830.
The U.S. Pat. No. 3,799,427 discloses a degassing valve for hermetically sealed flexible containers and a container provided with the valve. This valve has to be inserted into a preexisting opening in the wall of a container and part of the valve projects from the outer wall of the container. The German Patent document 2,360,126 is an equivalent to the U.S. Pat. No. 3,799,427.
The art cited above shows certain elements which may have relevance with respect to the elements of the present invention.